.
The time = = = hours = 3 hours and 20 minutes.
Since thy move toward each other, the relative speed is 30 = 60 = 90 km/h.
It means that the distance between them
decreasing at the rate of 90 miles per hour.
From the over side, yo know the formula time = .
In this way you get the final formula and the final result.
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On solving Travel and distance problems for two bodies moving toaward each other see the lessons
- Travel and Distance problems
- Travel and Distance problems for two bodies moving in opposite directions
in this site.